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    <script>
        /* 斐波那契数列 黄金比例数字
         1 1 2 3 5 8
        */
        function fn(n){
        if([1,2].includes(n)) return 1
        return fn(n-2)+fn(n-1)
        }
        const result = fn(4)
        console.log(result)
    </script>
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